1. Field of the Invention
The invention relates to the control of a vehicle, and more particularly, to the control of a hybrid vehicle.
2. Description of the Related Art
As the related art, there is known a hybrid vehicle that runs with the aid of a motive power of at least one of an engine and a motor. In the hybrid vehicle, as a rule, the storage amount of a battery for supplying an electric power to the motor is held within a predetermined range. For example, when the storage amount of the battery becomes equal to or smaller than a lower limit of the predetermined range, the engine is forcibly driven. The battery is charged with an electric power generated through the use of a driving force of the engine. As a result, the storage amount of the battery is restored.
However, when the engine is immediately started to charge the battery, inconveniences such as a deterioration in emission properties and the like occur because the engine and a catalyst for purifying exhaust gas from the engine have not been warmed up. Thus, the engine, the catalyst and the like need to be warmed up before the engine is started. An art concerning this warm-up is disclosed in Japanese Patent Application Publication No. 2003-269208 (JP-A-2003-269208).
A control apparatus disclosed in Japanese Patent Application Publication No. 2003-269208 (JP-A-2003-269208) is installed in a hybrid vehicle that runs with the aid of a driving force of at least one of an engine and a motor, and the engine is driven to charge a battery for supplying an electric power to the motor when the storage amount of the battery becomes equal to or smaller than a lower limit. This control apparatus heats the engine and a catalyst in advance by means of a heater when the storage amount of the battery becomes equal to a predetermined value larger than the lower limit. Thus, since the engine and the catalyst have already been warmed up when the engine is started, a deterioration in emission properties can be prevented. As a result, the vehicle can run appropriately.
Meanwhile, there has recently been developed a hybrid vehicle equipped with a battery that supplies an electric power to a motor and can be charged with an electric power from a power supply outside the vehicle, such as a household power supply or the like (hereinafter referred to also as “a plug-in hybrid vehicle).
The electric power from the household power supply is efficiently generated by an electric power company or the like. In general, therefore, the plug-in hybrid vehicle is designed to run using the electric power of the battery by priority.
For example, the running mode of the plug-in hybrid vehicle is set as a mode in which the vehicle runs by priority only with the aid of the motive power of the motor (hereinafter referred to also as “a charge depleting mode (CD mode)”) until the storage amount of the battery becomes smaller than a lower limit. A transition to a mode in which the vehicle runs using the motive power of the engine and the motive power of the motor (hereinafter referred to also as “a charge sustain mode (CS mode)”) is made when the storage amount of the battery becomes smaller than the lower limit.
In this plug-in hybrid vehicle, when the engine is started without warming up the catalyst during the transition to the CS mode, there is an apprehension for a deterioration in emission properties. Therefore, the catalyst is warmed up in advance during the CD mode prior to the transition to the CS mode, and the emission purification performance during the transition to the CS mode is thereby ensured. However, in the case where the vehicle is designed to warm up the catalyst with exhaust gas from the engine, the engine needs to be started to warm up the catalyst during the CD mode. The discharge amount of the battery decreases as a result of this startup of the engine. Thus, an actual running distance in the CD mode is longer than a distance recognized by a user, and a user feels a sense of incongruity.